mediatek: filogic: add support for Cudy WR3000S v1

mediatek: filogic: add support for Cudy WR3000S v1

Hardware
--------
MediaTek MT7981 WiSoC
256MB DDR3 RAM
128MB SPI-NAND (XMC XM25QH128C)
MediaTek MT7981 2x2 DBDC 802.11ax 2T2R (2.4 / 5)
UART: 115200 8N1 3.3V

MAC:
LAN MAC: label mac
WAN MAC: label mac + 1
2.4G MAC: label mac
5G MAC: label mac + 1 with LA bit set

Installation
------------

1. Connect to the serial port as described in the "Hardware" section.

2. Power on the device + press reset pin. Keep pressing reset pin to enter the U-Boot  shell.

3. Download the OpenWrt initramfs image. Place it on an TFTP server
   connected to the Cudy LAN ports. Make sure the server is reachable at
   192.168.1.88. Rename the image to "cudy3000s.bin"

4. Download and boot the OpenWrt initramfs image.

   $ tftpboot 0x46000000 cudy3000s.bin; bootm 0x46000000

5. Transfer the OpenWrt sysupgrade image to the device using scp.
   Install with sysupgrade.

Signed-off-by: David Ignjic <ignjic@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/16939
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>